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Numerical Study of the Three Gorges Dam Influences on Chlorophyll-a in the Changjiang Estuary and the Adjacent East China Sea.
- Source :
- Journal of Ocean University of China; Jan2021, Vol. 20 Issue 1, p10-22, 13p
- Publication Year :
- 2021
-
Abstract
- The impoundment of the Three Gorges Dam (TGD) has altered downstream hydrological characteristics and sediment discharge, and it has caused ecological impacts, such as changes in chlorophyll-a (Chl-a) in estuaries and coastal oceans. To investigate the TGD's influence on Chl-a's interannual and seasonal variations in the Changjiang Estuary and the adjacent coastal East China Sea, a physical-biogeochemical model was developed with numerical experiments covering a decade, including TGD's pre-period (pre-TGD, 1999–2003) and post-period (post-TGD, 2004–2008). The modeling results demonstrate an annual increase in the regional average Chl-a from pre- to post-TGD, with the largest increase reaching up to 20.8% in spring in the nearshore region beyond the Changjiang mouth. The spatial variations in Chl-a are high, with the largest variation being observed around the 20–40 m isobaths. The increase in Chl-a is influenced by improved light and nutrient conditions, which is attributed to dam construction and fertilization by human activities. A decline in nitrogen-phosphorus fertilizer usage ratio along the Changjiang River watershed after the TGD's impoundment is another factor that influences the Chl-a's variation. The modeling results also show severe NO<subscript>3</subscript> and PO<subscript>4</subscript> imbalances with a larger N/P ratio during the post-TGD period, especially in regions with large Chl-a increases. Moreover, the greater increase in the usage of phosphorus fertilizer than nitrogen fertilizer influences Chl-a's variation and has potential promotion effects on the outbreak of harmful algal bloom events. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 16725182
- Volume :
- 20
- Issue :
- 1
- Database :
- Complementary Index
- Journal :
- Journal of Ocean University of China
- Publication Type :
- Academic Journal
- Accession number :
- 148072665
- Full Text :
- https://doi.org/10.1007/s11802-021-4430-z